The prevalence and characteristics of co-occurring - Angelfire

14 Pages·2001·0.14 MB·English

Journal of Mental Health (2001) 10, 2, 175–188
The prevalence and characteristics of co-occurring
serious mental illness (SMI) and substance abuse or
dependence in the patients of Adult Mental Health
and Addictions Services in eastern Dorset
NICK VIRGO1, GERALD BENNETT1, DAVID HIGGINS1, LISA BENNETT1 &
PETER THOMAS2
1Dorset HealthCare NHS Trust & 2Bournemouth University, Bournemouth, Dorset, UK
Abstract
Researchers interviewed key workers of all NHS inpatient, day-patient and outpatient Adult Mental
Health (AMH, n=708) and Addictions (n=313) Services in eastern Dorset. ‘Dual diagnosis’ (co-
occurring severe mental illness (SMI) and substance abuse or dependence) occurred in 12% of
addictions, 12% of all AMH, and 20% of SMI, AMH patients (range 10% rehabilitation to 41% acute
wards). Most ‘dual diagnoses’ in AMH were alcohol and/or cannabis abuse with psychoses, and in
addictions heroin dependence and/or alcohol abuse or dependence with depression. Compared with
other AMH, SMI patients, AMH ‘dual diagnosed’ patients were younger; were more often male, in less
stable accommodation, unemployed, with more than one psychiatric diagnosis and personality
disorder; and tended to have more crises and pose greater risk to themselves and others. Compared
with ‘dual diagnosed’ addictions patients they were less involved with drugs, at less risk of abuse by
others and less often acknowledged dual problems.
Introduction over one third of people with alcohol disor-
ders and over half of people with drug disor-
Little is known about the UK prevalence of ders had experienced at least one mental
substance use disorders in seriously mentally disorder in their life. Among a sub-sample
ill (SMI) patients, or how SMI patients mis- drawn from mental health treatment settings,
using substances differ from those who do Regier et al. (1990) found a 37% lifetime
not. Far more research has been conducted in prevalence of alcohol abuse and a 20% 6-
North America, including two large, multi- month prevalence of substance abuse (alco-
centre community studies. Among all people hol 14%, drugs 8%). Reviewing other US
with mental illness, Kessler et al. (1996) prevalence studies, Mueser et al. (1995) found
found a 15% 12-month prevalence of sub- that most had shown that between 25% and
stance abuse and Regier et al. (1990) an 11% 35% of people in treatment settings and with
6-month and 29% lifetime prevalence. Also, severe mental illness (SMI), had had a sub-
Address for Correspondence: Nick Virgo, Department of Psychological Therapies, Herbert Hospital, Alumhurst
Road, Bournemouth BH4 8EW, UK. Tel: [phone]; Fax: [phone]; nick.virgo@dorsethc-
tr.swest.nhs.org.uk
ISSN 0963-8237print/ISSN 1360-0567online/2001/0200175-14 © Shadowfax Publishing and Taylor & Francis Ltd
DOI: 10.1080/09638230020023732
176 Nick Virgo et al.
stance use disorder in the past 6 months. and substance use and dependence are pre-
American mental health patients who misuse sented by Meltzer et al. (1996a,b) and by
substances have worse functioning in mental Farrell et al. (1998). The results of a private
health, social stability, treatment compliance, household survey and a survey of hospitals,
legal problems, HIV infection and family hostels and residential homes illustrate quan-
stress than others (Drake & Brunette, 1998; tities consumed rather than problems. They
Osher & Drake, 1996). The generalisability found that 7% of people with schizophrenia,
of these findings to the UK is undetermined, 18% with affective disorders and 22% with
given important differences between the two neurotic disorders reported ever using drugs.
nations including their patterns of substance Examining alcohol, they found that 16% of
use and their mental health and addictions people with schizophrenia, 18% with affec-
services. tive disorder and 21% with neurotic disorder
British studies have been limited to inner had been drinking over the recommended
city London or very select SMI populations limits for the normal population, 14 standard
or have approached substance misuse from units a week for women and 21 for men. The
examining consumption rather than conse- sample was of people in stable institutional
quences. Duke et al. (1994) found a 22% care (not exclusively specialist treatment set-
lifetime prevalence of alcohol abuse in peo- tings), which did not include acute care. It is
ple with schizophrenia living in the South thus reasonable that the figures are lower
Westminster area of London, including those than those from other studies of people in
not in contact with mental health treatment treatment settings.
services. In Camberwell London, in 171 This non-metropolitan UK study aimed to
people with any psychotic illness who were establish the lifetime and point prevalence of
younger and all drawn from mental health substance abuse and dependence among all
treatment services, Menezes et al. (1996) current SMI patients of all services of an
found a 42% lifetime prevalence of alcohol NHS Trust, not just those with psychosis and
abuse, which is comparable to the 37% of including those of specialist addiction serv-
Regier et al. (1990). Examining 12-month ices; to assess how far US-found differences
prevalence, they found 36% for any sub- between substance misusing and other SMI
stance abuse (alcohol 32%, drugs 16%) and patients occurred in this sample; and to detect
draw comparison with the very close results differences between ‘dually diagnosed’ pa-
of a study in New England (Drake & Wallach, tients of specialist addictions services and
1989), which used the same method of case those of other adult mental health services.
identification.
Cantwell et al. (1999) found a 37% 12- Method
month prevalence of drug use or drug or
alcohol misuse in first episode psychosis The study was carried out in an NHS Trust
patients in Nottingham. This study did not serving a community on the south coast of
use the DSM based definitions used in the England. The population of 450,000 in-
two aforementioned studies but included any cludes a large conurbation (of Bournemouth,
drug use of at least once per month in the Poole and Christchurch) surrounded by a
preceding year. The National Psychiatric rural belt of small market towns (e.g.
Morbidity Survey in England results as they Wimborne) and holiday resorts (e.g.
relate to co-occurrence of mental disorder Swanage). The AMH Service for this com-
Prevalence of substance misuse in SMI 177
munity consisted of seven multidisciplinary, were to be discussed. They were encouraged
specialist Community Mental Health Teams to read the case notes beforehand and to bring
(CMHTs) linked to primary health care teams, them to the interview. Interviews took about
an acute hospital, residential and day treat- 60 minutes and covered an average of 12
ment and rehabilitation units, and a group patients.
therapy treatment unit. The Addictions Serv-
Statistical analysis
ice provides community drug and alcohol
teams, a detoxification ward and an absti- The principal aim was to compute the over-
nence-oriented, day treatment unit for sub- all prevalence of co-occurring serious men-
stance dependence. tal illness and substance abuse or dependence
together with its 95% Confidence Interval
Design
(CI) and then to do the same for each compo-
To establish (A) what proportion of the nent of the services. To compensate for the
current patients of an NHS Trust’s (1) Adult fact that CMHTs were underrepresented, a
Mental Health (AMH) and (2) specialist Ad- weighted analysis was carried out when data
dictions Services were currently diagnosed from the different CMHTs were combined,
with or met the criteria for a severe mental with or without data from the other services
illness (SMI) and (B) what proportion of (Lee et al., 1989). Patients studied in each
those SMI patients had current substance CMHT were weighted by the inverse of the
abuse or dependence, thus calculating the probability with which they were sampled in
point prevalence of ‘dual diagnosis’ in each order to ensure that the estimates of preva-
arm of the service. To then compare charac- lence were not biased by the sampling strat-
teristics of (C) AMH SMI patients with cur- egy. The analysis was carried out using SPSS
rent substance abuse or dependence with for Windows Version 6.1 (Norusis, 1993).
AMH SMI patients without and (D) AMH For each analysis the weights were standard-
‘dual diagnosis’ patients with addictions serv- ized by dividing by a constant (total number
ice ‘dual diagnosis’ patients. had all patients been included ¸ total number
Information was gathered on all persons actually sampled) which ensured that the
who, on a specific day (15.01.97), were pa- total number of cases in each weighted analy-
tients of any of the Trust’s services except in sis was equivalent to the total number of
the case of its seven Community Mental cases actually studied and eligible to be in-
Health Teams (CMHTs) whose 2612 pa- cluded (Lee et al., 1989). This technique
tients were too many to study in total. A helps to ensure that realistic estimates of
random sample of 60 patients of each CMHT standard error and results of hypothesis tests
was selected from all those registered for the are obtained from the package (Norusis,
Care Programme Approach (CPA) with that 1993).
CMHT. Information was gathered from the Two sets of comparisons were made (see
professional (‘key worker’) responsible for Design, C and D), each involving two groups
co-ordinating the care of each patient using a and testing two similar hypotheses on each
structured interview and standardized rating variable. To reduce the overall chance of
scales. making a Type I error, for each variable a
Several weeks in advance of being inter- Bonferroni adjusted significance level of
viewed key workers were informed of the 0.025 was used. No further adjustment was
nature of the project and told which patients made for the number of variables tested.
178 Nick Virgo et al.
Means of normally distributed variables were 1996) for alcohol and other drugs separately.
compared using the independent samples t- The scale is based on DSMIII-R definitions
test. For variables measured on a nominal (American Psychiatric Association, 1987)
scale, the groups were compared using the and has demonstrated high validity and reli-
chi-squared test for association. If the vari- ability (Drake et al., 1989, 1990; Mueser et
able could be ordered, the chi-squared test for al., 1995). Current status was determined by
linear trend was used (Breslow & Day, 1980). the highest point of the scale occupied for a
Researchers first established whether the period of one month or more during the
patient had an SMI, either with or without a preceding six months (Drake et al., 1996).
functional psychosis, according to the defini-
tion of the Department of Health’s Building
Results
Bridges report (Department of Health, 1996).
This definition, which can include any Axis Prevalence of serious mental illness
I disorder as an SMI depending on the pa-
Key workers were interviewed about 1021
tient’s diagnosis and level of disability, vul-
(87%) of the targeted 1177 patients. The
nerability, risk and need for care, is broader
numbers of patients investigated and cover-
than the strict diagnoses of psychoses used as
age rates N (%) were acute hospital, 98
an analogue of SMI in other studies (Menezes
(100%), rehabilitation, 189 (98%), group
et al., 1996; Duke, et al., 1994). Such
therapy unit, 79 (69%), CMHTs, 342 (81% of
inclusiveness combined with ease of applica-
the target sample) and addictions, 313 (89%).
tion made it better suited to this study of a full
range of NHS care settings. Patients with Of the total 1021 patients, 55% (CI 52–
current substance abuse or dependence and/ 58%) had a confirmed SMI and 44% (CI 41–
47%) had a confirmed SMI with functional
or personality disorder were classified SMI
only if they also met the criteria of a co- psychosis. Some 56% (CI 53–59%) had
either or both of these and are henceforth
morbid Axis I disorder. No further informa-
described as the ‘SMI’ group. The preva-
tion was collected for patients who did not
lence of SMI with 95% CI are reported for
meet the criteria for SMI.
each part of the service in Table 1.
The continued interview recorded psychi-
atric diagnoses, time in current treatment,
Characteristics of the 510 SMI patients
housing situation and employment status.
On seven-point, ordinal scales for the previ- Because of missing data all of the follow-
ous 6 months, key workers then rated the ing summaries are based on 500 patients,
number of crises leading to additional inter- except for age, which is based on 496.
vention; risk to self and others and risk of The mean age of the SMI patients was 42
abuse by others; overall level of disablement years (SD 12 range 17–67) and half (50%)
resulting form mental illness; and need for were male.
formal and informal care. The most commonly reported diagnoses
Key workers then reported lifetime prob- were schizophrenia 52% (CI 48–56%); de-
lems with alcohol or other drugs, the drugs pression 17% (CI 14–20%); bipolar disorder
‘misused’ during the previous 6 months, and 12% (CI 9–15%); schizo-affective disorder
current status as either abstinence, non-prob- 10% (CI 8–13%); anxiety 7% (CI 5–10%);
lematic use, abuse or dependence according obsessive-compulsive disorder 4% (CI 2–
to the Clinician Rating Scale (Drake et al., 6%); personality disorder 2% (CI 1–4%); and
Prevalence of substance misuse in SMI 179
Table 1: Point prevalence of (a) Serious Mental Illness (SMI) and (b) Co-occurring SMI and
substance abuse or dependence (based on the preceding six months) in the Addictions
Service and in each component of the Adult Mental Health (AMH) services
Serious mental illness Co-occurring disorder
Component of Service N % 95% CI N % 95% CI
Addictions (n=313) 44 14 10–18 38 12 9–16
Acute Hospital (n=98) 66 67 58–77 27 28 19–37
Rehabilitation Service (n=189) 184 97 95–100 18 10 5–14
Group Therapy Unit (n =79) 1 1 0–4 0 0 0
CMHT1 A (n=55) 25 45 32–59 4 7 2–14
CMHT B (n=60) 45 75 64–86 13 22 11–32
CMHT C (n=46) 33 72 58–85 7 15 4–26
CMHT D (n=57) 24 42 29–55 4 7 2–15
CMHT E (n=29) 18 62 43–81 4 14 1–27
CMHT F (n=38) 28 74 59–88 3 8 0–17
CMHT G (n=57) 42 74 62–85 5 9 1–8
Total of CMHTs (n =342) 60 55–65 12 10–15
Total (n=1021) 56 53–59 12 10–14
1 Community Mental Health Team
adjustment reaction 2% (CI 1–3%). The ment 5%, student 3%, sheltered employment
majority had been in treatment for more than 3% and retirement 2%.
6 months. A third, (CI 29–37%) of SMI patients had
The usual accommodations for SMI pa- in their lifetime abused or been dependent on
tients had been their own home 34%, shel- alcohol or other drugs. Examining alcohol
tered accommodation 18%, their parents’ and other drugs separately, 23% (CI 19–
home 16%, privately rented accommodation 27%) had a lifetime history of abuse or de-
11%, local authority rented accommodation pendence on alcohol, while 22% (CI 18–
10%, an institution or hospital 6%, a bed sit 25%) had a lifetime history of abuse or de-
4% and lodgings 2%. pendence on other drugs. The Clinician
The SMI patients main employment or Rating Scale measures of SMI patients’ cur-
source of income had been disability benefit rent involvement with alcohol and other drugs,
46%, unemployment 27%, housewife 10%, based on the preceding 6 months, are summa-
part-time employment 6%, full-time employ- rized in Table 2. Key workers reported that
Table 2: Rating of current substance use, based on the preceding 6 months, in the (a) 510
Seriously Mentally Ill (SMI) patients and (b) the 123 who also had substance abuse or
dependence (SMI+)
Alcohol Drugs Alcohol or drugs
SMI SMI+ SMI SMI+ SMI SMI+
Abstinent 73% 26% 81% 33% 66% -
Non-problematic use 14% 16% 5% 4% 12% -
Abuse 9% 42% 11% 50% 16% 74%
Dependence 4% 16% 3% 13% 6% 26%
180 Nick Virgo et al.
Table 3: Current problematic use (abuse or dependence) of alcohol and other drugs, based on
the preceding 6 months, in the 510 seriously mentally ill (SMI) patients in each
component of the services
Service Problem with Problem with Problem with
alcohol other drugs alcohol or other drugs
% 95% CI % 95% CI % 95% CI
Addictions n= 44 41 (26–56) 80 (67–92) 86 (76–97)
Adult mental health n=4661 12 (9–15) 12 (9–15) 20 (17–24)
Rehabilitation n=184 7 (3–11) 5 (2–9) 10 (5–14)
Acute hospital n=66 21 (11–31) 33 (22–45) 41 (29–53)
Community Mental Health Teams
n=215 12 (8–17) 12 (7–16) 21 (15–26)
Note: 1 The total includes one patient of the Group Therapy Unit
most patients had abstained from both alco- have a problem with alcohol only, 42% with
hol and other drug use, that most problematic other drugs only and a fifth, (21%), with both
use was abuse rather than dependence and alcohol and other drugs.
that there was little difference between levels In addition to completing Clinician Rating
of problem use of alcohol and problem use of Scales for alcohol and other drugs, key work-
other drugs. ers indicated from a checklist the drugs they
believed each SMI patient had ‘misused’ in
Prevalence of co-occurring serious
the preceding 6 months. Half were reported
mental illness and substance abuse or
to have misused one drug only (including
dependence
alcohol), 34% two drugs, 4% three, 6% four
Some 22% (CI 19–26%) of the 510 SMI and 5% five or more. Those most commonly
patients were reported, on the basis of the reported were alcohol 74% (CI 65–81%);
preceding 6 months, to have current abuse or cannabis 40% (CI 32–49%); prescription
dependence on alcohol or other drugs and drugs 17% (CI 10–24%); amphetamines 12%
thus a ‘dual diagnosis’. The proportions of (CI 6–18%); opiates 10% (CI 5–16%);
those 510 SMI patients are reported sepa- benzodiazepines 10% (CI 4–15%); sedative-
rately for alcohol and other drugs in different hypnotics 8% (CI 3–13%); over-the-counter
parts of the Trust and are shown in Table 3. medications 2% (CI 0–5%); MDMA 3% (CI
The prevalence of co-occurring problems in 0–6%); and LSD 2% (CI 0–6%).
the total sample of 1021 patients was 12% (CI
Comparisons between adult mental
10–14%) and those in different parts of the
health severely mentally ill patients with
Trust are summarized in Table 1. The preva-
and without substance abuse or depend-
lence in AMH was identical to that in the
ence
Addictions Service (12%).
Patients with co-occurring problems tended
Nature of substance problems in SMI
to be younger (respective means 35.9 years v.
patients with substance abuse or de-
43.9 years, t=5.9, df=440, p<0.0001) and
pendence
were more often male (65% v. 47%, c 2=8.4,
Just over a third (37%) of the 123 patients df=1, p<0.01) and unemployed (40% v. 24%,
with co-occurring problems were reported to c 2=8.1, df=1, p<0.01).
Prevalence of substance misuse in SMI 181
Table 4: Diagnoses of SMI patients with and without current substance abuse or dependence
based on the preceding 6 months
AMH SMI AMH SMI Addiction SMI
patients without patients with with substance
substance misuse substance misuse misuse
n=370 Contrast 1 n=85 n=38 Contrast 2
Schizophrenia 54% 52% 5% 8.7**
Schizo-affective disorder 12% 6% 5%
Bipolar disorder 11% 16% 5%
Psychotic episodes 1% 2% 3%
Depression 14% 23% 66% 9.2**
Anxiety 7% 7% 29%
Obsessive-compulsive disorder 5% 1% 11%
Adjustment reaction 2% 2% 5%
Anorexia nervosa 1% 2% 5%
Paranoid ideas 0% 2% 3%
Personality disorder 1% 7.7** 7% 5%
Note:
People with personality disorder were classified SMI only if there was a co-occurring Axis I
disorder besides substance abuse or dependence.
Contrast 1 compares AMH SMI patients who either had or did not have a substance abuse or
dependence.
Contrast 2 compares AMH SMI patients with a substance abuse or dependence against the same
addictions service patients. Each contrast was computed using the c 2 test, and values of this
statistic are only given when these are significant at the 0.025 level; ** p<0.01
Patients with co-occurring problems were other drugs (63% v. 37%, c 2=120.3, df=1,
more likely to have lived with friends (7% v. p<0.00001).
1% c 2=10.0, df=1, p<0.01) or in privately By definition SMI patients with co-occur-
rented accommodation (19% v. 8%, c 2=9.1, ring problems were more involved with alco-
df=1, p<0.01) and less likely to have lived in hol or other drugs, the Clinician Rating Scale
their own home (18% v. 39%, c 2=12.9, df=1, reflecting the most severe level of use for a
p<0.001) in the preceding 6 months. period of 1 month during the preceding 6
Patients with co-occurring problems were (Table 5). For all SMI patients, key workers
more likely to have more than one psychiatric also reported all those checklist drugs ‘mis-
diagnosis besides substance abuse or depend- used’ in the preceding six months. Patients
ence (15% v. 7%, c 2=5.1, df=1, p<0.025) and with co-occurring problems were more likely
to have a personality disorder (7% v. 1%, to have ‘misused’ both alcohol (73% v 14%,
c 2=7.7, df=1, p<0.01). Table 4 illustrates df) and cannabis (39% v 4%, df). Further c 2
diagnostic differences between groups of SMI tests were not performed because of small
patients. numbers: the frequency of reports of ‘mis-
Patients with co-occurring problems were use’ by patients without co-occurring prob-
more likely to have reported a lifetime his- lems being less than 0.5% for each of the
tory of abuse or dependence on alcohol (72% other drugs. The frequencies of ‘misuse’ of
v. 10%, c 2 = 152.5, df = 1, p<0.00001) and/or other drugs by SMI AMH patients with co-
182 Nick Virgo et al.
occurring problems were not significantly significant differences between the two groups
different to those reported in the previous in either their housing (c 2=11.1, df=8, NS) or
section (nature of substance problems) apart usual employment or source of income
from opiates. (c 2=4.9, df=7, NS).
The distribution of the number of crises The two groups did not differ significantly
leading to more treatment according to key in their number of psychiatric diagnoses (c 2
workers reports on the ordinal scale was test for linear trend 2.6, df=1, NS) but addic-
skewed, with 52% of patients having no tions patients were more likely than AMH
crises in the preceding 6 months. However patients to be diagnosed with depression and
those with co-occurring problems tended to less likely to be diagnosed with schizophre-
have more crises (c 2 test for linear trend 18.9, nia (Table 4). There was no significant
df=1, p<0.00001). The respective percent- difference between the two groups for time in
ages of patients with and patients without co- current treatment (c 2 test for linear trend 4.7,
occurring problems who had experienced the df=1, NS).
following numbers of crises leading to addi- Abuse or dependence on alcohol or other
tional treatment in the previous 6 months drugs
were; none, 31%, 57%; one, 27%, 21%; The two groups did not differ significantly
two,13%, 7%; three, 11%, 4%; four or more, in frequency of past abuse or dependence on
18%, 10%. either alcohol (c 2=0.6, df=1, NS) or other
Key workers rated patients with co-occur- drugs (c 2=4.3, df=1, NS). However, com-
ring problems at greater risk to themself than pared to AMH patients, addictions patients
those without (c 2 test for linear trend 20.5, had significantly greater current involvement
df=1, p<0.0001): and also at greater risk to in drugs (c 2 test for linear trend 16.3, df=1,
the safety of others (c 2 test for linear trend p<0.0001) but not alcohol (c 2 test for linear
11.2, df=1, p<0.001). trend 0.0, df=1, NS), summarised in Table 5.
Key workers’ ratings of patients’ current Addictions patients were more often reported
levels of personal and social disability arising to be misusing more than one type of drug
from their mental illness did not differ sig- (84% v. 44%, c 2=6.2, df=1, p<0.025) but
nificantly between groups (c 2 test for linear there were higher rates of reported misuse of
trend 1.6, df=1, NS). only one of the13 drugs considered: opiates
Key workers’ ratings did not differ signifi- (62% v. 5%, c 2=33.8, df=1, p<0.0001).
cantly between groups on either needing for- More addictions than AMH patients (90%
mal (c 2 test for linear trend 2.4, df=1, NS) or v. 8%) were prescribed methadone (c 2=27.9,
informal (c 2test for linear trend 4.3, df=1, NS) df=1, p<0.00001).
care. Key workers judged whether or not pa-
tients recognised that they had both a mental
Comparisons between those ‘dual
illness and a substance misuse problem. A
diagnosis’ patients served by the Adult
significantly greater proportion of the addic-
Mental Health Service and those served
tions patients (84%) than AMH patients (37%)
by the Addictions Service
did so (c 2=9.1, df=1, p<0.01).
The mean age for both groups was 36 The two groups did not differ significantly
(t=0.2, df=115, NS). Males made up 65% of (c 2 test for linear trend 0.9, df=1, NS) on
the AMH patients and 32% of the addictions crises leading to more treatment.
patients (c 2=4.2, df=1, NS). There were no Key workers’ ratings did not differ signifi-
Prevalence of substance misuse in SMI 183
Table 5: Current degree of involvement in alcohol or other drugs, based on the preceding 6
months, by groups of SMI patients
AMH SMI without AMH SMI with Addiction SMI with
substance misuse substance misuse substance misuse
n=370 n=85 n=38
(a) Alcohol
Abstinent 87% 26% 26%
Non-problematic use 13% 14% 26%
Abuse - 44% 24%
Dependence - 16% 24%
(b) Other drugs
Abstinent 95% 36% 5%
Non-problematic use 5% 5% 3%
Abuse - 53% 21%
Dependence - 6% 71%
cantly between groups on either risk to self stance use problems were found in one in
(c 2 test for linear trend 2.8, df=1, NS) or to eight of all patients using AMH services. The
others (c 2 test for linear trend 2.4, df=1, NS). size of the sample allowed estimates of preva-
Key workers’ ratings of level of risk of lence to be made with a reasonable degree of
abuse by others were higher for Addictions confidence.
than AMH patients (c 2 test for linear While these prevalence rates are lower than
trend=12.7, df=1, p<0.001): the median (and those reported from some British and North
inter quartile ranges) for the former was 5 (3) American studies they do represent a prob-
and for the latter was 3 (2). lem of significant size. There are also simi-
Ratings of patients’ current levels of per- larities between some of our results and some
sonal and social disability arising from their of the other UK and US studies. Duke et al.
mental illness did not differ significantly (1994) found that 22% of their community
between groups (c 2 test for linear trend 4.8, sample had a lifetime history of alcohol abuse,
df=1, NS) the present study found 23% in. Regier et al.
Ratings did not differ significantly between (1990) found a 20% 6-month prevalence of
groups in need for either formal or informal substance misuse in their community sub-
care. sample drawn from mental health treatment
settings, the present study found a 20% preva-
Discussion lence in SMI AMH patients. Cantwell et al.
(1999) found a 37% 12-month prevalence in
Prevalence
first-episode psychosis patients, the present
Problematic use of mood altering substances study found 41% prevalence in AMI acute
was found in one in five seriously mentally ill hospital patients. Menezes et al. (1996) found
(SMI) patients using Adult Mental Health lifetime and 12-month prevalence rates that
(AMH) Services within the previous 6 months. were higher than those from the correspond-
One in three SMI patients had experienced ing SMI AMH group from the present study.
problematic substance use in their lifetimes. That the prevalence of co-occurring disor-
The co-occurring problems of SMI and sub- ders varied considerably within the care sys-
184 Nick Virgo et al.
tem, from 10% of rehabilitation patients and dependence is rare, medical interventions
12% of CMHT patients to 28% of patients in (e.g. detoxification), and psychological treat-
the acute hospital (and 41% of SMI patients ment approaches based on models of depend-
there), to some extent represents the ways in ence (e.g. disease concept) may seem to be
which patients are managed. For example largely inappropriate and therefore patients
mentally ill patients who live in residential may be best treated in mental health rather
rehabilitation facilities are more closely moni- than addictions services.
tored than those living in the community and This is the first British study to examine the
have less opportunity to purchase or ingest prevalence of co-occurring disorders in a
illicit mood altering drugs. These figures specialist addictions service. It is interesting
may also represent the ways in which the that this prevalence was identical to that
misuse of drugs exacerbate mental illness observed in the specialist mental health serv-
and make it more likely that substance SMI ices. That patients of addiction services
patients using alcohol and other drugs will display high levels of psychopathology is not
soon need an acute bed. Estimating the new but SMI is unexpected, especially given
prevalence of co-occurring problems just by that most patients with a primary problem of
investigating patients in acute wards would severe mental illness would be likely to present
give an inflated estimate, reflecting Berkson’s at mental health services. It will be important
fallacy (Berkson, 1949): estimates of the to investigate further the types of SMI ap-
prevalence of co-occurrence are inflated when pearing in addiction services and the pathway
studies examine samples from treatment serv- which led them in.
ices rather than the general population (since
Co-morbid patients have greater
the probability that persons will receive treat-
problems
ment will be increased by either disorder).
Berkson’s fallacy implies that the prevalence Patients with dual disorders tended to have
of co-occurrence will be greater in services more extensive and more severe problems
for acutely ill patients than in those providing than those without. Consistent with North
longer term care. American studies this group posed more risks
Most problematic substance use in patients to themselves and others, and more demands
of the mental health services was abuse rather on services (in terms of crisis interventions),
than dependence. It is not clear to what extent thus justifying concern about them. The
abuse has the capacity to stimulate and exac- finding that they posed greater risk to others
erbate mental illness, although some have is consistent with the British study that found
argued from the stress-vulnerability perspec- higher levels of aggressive behaviour in the
tive (Zubin & Spring, 1977) that patients with co-morbid group (Scott et al., 1998). The
SMI are likely to experience adverse conse- interesting failure to find differences in key
quences from ingesting relatively small workers’ ratings of need for formal and infor-
amounts of mood altering substances. In a mal care, and disability arising from the men-
recent review of the status of etiologic theo- tal illness was inconsistent with US research.
ries of co-occurrence, Mueser et al. (1998) It is difficult to interpret the findings about
concluded that there is support for this super- the association between personality disorder
sensitivity model that implies that any use with substance use disorder, since personal-
has the capacity to harm the health of se- ity disorders are probably not routinely diag-
verely mentally ill persons. To the extent that nosed with the same rigour as Axis 1 disor-